N102-135 TITLE: Rain Repellency for Shipboard Aircraft Transparency

TECHNOLOGY AREAS: Air Platform

ACQUISITION PROGRAM: Joint Strike Fighter, ACAT I

OBJECTIVE: Develop innovative rain repellency coating concepts for aircraft stretched acrylic canopies to improve visibility in inclement weather.

DESCRIPTION: Navy aircraft often have to taxi, take-off, and land during conditions of differing amounts of rain. While performing taxi and take-off operations the pilot must be able to clearly see ground crew directions. During landing, the pilot must be able to clearly see landing strip lights, and for carrier landings, the Optical Landing System (OLS). The Joint Strike Fighter canopy and windscreen are manufactured from stretched acrylic in accordance with MIL-P-25690 and has a polyurethane-type top coat.

Development of innovative concepts for permanent coatings to improve rain shedding properties for ground and low speed operations are desired. Rain repellent evaluations of Commercial Off The Shelf (COTS) hydrophobic treatments, used in automotive and non-aviation marine applications, showed little to no margin of improvement over the baseline coating system. These evaluations were conducted at room temperature in laboratory conditions using a roll-angle test. Proposed coating concepts must be compatible with the polyurethane-type top coat, mission environments (i.e. supersonic speeds, and extreme temps) and should last the life of the aircraft transparency without degradation. Chronically applied coatings or treatments that would perform the same task will also be considered. Treatment solutions must be able to meet requirements specified in "Rain Repellency Coating Requirements", listed below. These requirements include, but are not limited to: rain erosion, marine operating environment, salt fog, salt spray and commonly encountered chemicals. Coatings and treatments may not hinder the optical properties in any way, including haze, optical distortion, and light transmissivity.

PHASE I: Determine feasibility of developing a permanent or chronically applied rain repellency coating to perform in a marine environment on stretched acrylic transparencies with polyurethane-type top coats.

PHASE II: Demonstrate the validity of the Phase I approach through fabrication and testing of sub-scale coupons. Coated coupons should be tested against bare stretched acrylic, and polyurethane-type coated acrylic. Coupons should be tested by measuring the roll angle before and after rain erosion testing, as well as before and after being subjected to salt spray.

PHASE III: Transition the approach to a qualified transparency vendor for use on military and commercial aircraft.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Successfully developed technologies have potential to transition to the commercial aircraft market. In addition, the automotive aftermarket may also be interested in this type of coating.

REFERENCES:
1. MIL-PRF-25690B � PLASTIC, SHEETS AND FORMED PARTS, MODIFIED ACRYLIC BASE, MONOLITHIC, CRACK PROPAGATION RESISTANT

2. "Rain Repellency Coating Requirements", Document Number 435-001-2010.2, 23 Sept 2009, posted in SBIR Interactive Topic Information System (SITIS) on 04/30/10.

KEYWORDS: Transparency; Rain Repellency; Optically Clear; Polymer Materials; Coating; Acrylic Treatment

** TOPIC AUTHOR (TPOC) **

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